The present invention relates to an electrolyte, an ion conductor including the electrolyte, and electrochemical devices including the electrolyte, such as lithium cells, lithium ion cells, electrical double-layer capacitors.
Accompanying the evolution of portable equipment in recent years, there has been active development of electrochemical devices utilizing electrochemical phenomena, such as cells for use as their power supplies and capacitors. In addition, electrochromic devices (ECD), in which a color change occurs due to an electrochemical reaction, are examples of electrochemical devices for uses other than power supplies.
These electrochemical devices are typically composed of a pair of electrodes and an ion conductor filled between them. The ion conductor contains a salt (AB) as an electrolyte, which is dissolved in a solvent, polymer or mixture thereof such that the salt is dissociated into cations (A+) and anions (Bxe2x88x92), resulting in ionic conduction. In order to obtain the required level of ion conductivity for the device, it is necessary to dissolve a sufficient amount of this electrolyte in solvent or polymer. In actuality, there are many cases in which a solvent other than water is used, such as organic solvents and polymers. Electrolytes having sufficient solubility in such organic solvents and polymers are presently limited to only a few types. For example, electrolytes having sufficient solubility for use in lithium cells are only LiClO4, LiPF6, LiBF4, LiAsF6, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9) and LiCF3SO3. Although the cation type of the electrolyte is frequently limited by the device as is the case with the lithium ion of lithium cells, any anion can be used for the electrolyte provided it satisfies the condition of having high solubility.
Amidst the considerable diversity of the application range of these devices, efforts are made to seek out the optimum electrolyte for each application. Under the present circumstances, however, optimization efforts have reached their limit due to the limited types of available anions. In addition, existing electrolytes have various problems, thereby creating the need for an electrolyte having a novel anion portion. More specifically, since ClO4 ion of LiClO4 is explosive and AsF6 ion of LiAsF6 is toxic, they cannot be used for reasons of safety. Even the only practical electrolyte of LiPF6 has problems including heat resistance and hydrolysis resistance. Although electrolytes of LiN(CF3SO2)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9) and LiCF3SO3 are stable and high in ionic conductivity, they corrode the aluminum collector inside the cell when a potential is applied. Therefore, their use presents difficulties.
It is therefore an object of the present invention to provide a useful novel electrolyte, a novel ion conductor containing the electrolyte, and a novel electrochemical device containing the ion conductor.
According to the present invention, there is provided an electrolyte for an electrochemical device. This electrolyte comprises:
a first compound that is an ionic metal complex represented by the general formula (1); and
at least one compound selected from the group consisting of second to fourth compounds respectively represented by the general formulas (2) to (4), fifth to ninth compounds respectively represented by the general formulas Aa+(PF6xe2x88x92)a, Aa+(ClO4xe2x88x92)a, Aa+(BF4xe2x88x92)a, Aa+(AsF6xe2x88x92)a, and Aa+(SbF6xe2x88x92)a, and tenth to twelfth compounds respectively represented by the general formulas (5) to (7), 
xe2x80x83wherein M is a transition metal selected from the group consisting of elements of groups 3-11 of the periodic table, or an element selected from the group consisting of elements of groups 12-15 of the periodic table;
Aa+ represents a metal ion, hydrogen ion or onium ion;
a represents a number from 1 to 3; b represents a number from 1 to 3; p is b/a; m represents a number from 1 to 4; q is 0 or 1;
R1 represents a C1-C10 alkylene group, C1-C10 halogenated alkylene group, C4-C20 arylene group or C4-C20 halogenated arylene group, these alkylene and arylene groups of said R1 optionally having substituents and hetero atoms, one of said R1 being optionally bonded with another of said R1;
each of X1 and X2 independently represents O, S or NR2;
R2 represents a hydrogen, C1-C10 alkyl group, C1-C10 halogenated alkyl group, C4-C20 aryl group or C4-C20 halogenated aryl group, these alkyl and aryl groups of said R2 optionally having substituents and hetero atoms, at least two of said R2 being optionally bonded together to form a ring;
each of x, y and z independently represents a number from 1 to 8
each of Y1, Y2 and Y3 independently represents a SO2 group or CO group; and
each of R3, R4 and R5 independently represents an electron-attractive organic substituent optionally having a substituent or a hetero atom, at least two of said R3, R4 and R5 being optionally bonded together to form a ring, at least one of said R3, R4 and R5 being optionally bonded with an adjacent molecule to form a polymer.
According to the present invention, there is provided an ion conductor for an electrochemical device. This ion conductor comprises the electrolyte; and a member selected from the group consisting of a nonaqueous solvent, a polymer and a mixture thereof, said member dissolving therein said electrolyte.
According to the present invention, there is provided an electrochemical device comprising (a) first and second electrodes; and (b) the ion conductor receiving therein said first and second electrodes.